The sequence makes no difference as long as you do a thorough job. Brushing and flossing is the best way to remove decay-causing plaque from your teeth and help maintain optimal oral health.
Choose a toothbrush that feels comfortable in your hand and in your mouth, and use it twice a day. Place your toothbrush at a 45-degree angle against the gums. Move the brush back and forth gently in short (tooth-wide) strokes brushing the outer tooth surfaces, the inner tooth surfaces, and the chewing surfaces of the teeth as well as the inside surfaces of the front teeth.
While tooth brushing removes plaque from tooth surfaces, it can't do the entire job of removing plaque. Cleaning between the teeth daily with floss removes debris from between the teeth where your toothbrush cannot reach. People who have difficulty handling dental floss may prefer to use another kind of interdental cleaner. These aids include special brushes, picks or sticks. If you use interdental cleaners, ask your dentist about how to use them properly to avoid injuring your gums.
How do you know if you're doing a thorough job? Your dentist may recommend using plaque disclosing tablets available over-the-counter at pharmacies and other stores that sell oral hygiene products. Plaque disclosing tablets are chewed after you clean your mouth. Red dye will stain plaque that has not been removed, showing you spots that need additional cleaning.